Homeland Security Articles

Ten-Fold Increase in Frequency of Katrina-Magnitude Storms this Century

Tropical cyclones arise over warm ocean surfaces with strong evaporation and warming of the air. Since 1923, there has been a Katrina magnitude storm surge every twenty years. Researchers found that 0.4 degrees Celcius warming of the climate corresponds to a doubling of the frequency of extreme storm surges like the one following Hurricane Katrina. If the temperature rises an additional degree, the frequency will increase by 3-4 times, and if the global climate becomes two degrees warmer, there will be about ten times as many extreme storm surges.

By examining the frequency of extreme storm surges in the past, previous research has shown that there was an increasing tendency for storm hurricane surges when the climate was warmer. How much worse will it get, however, as temperatures rise in the future? How many extreme storm surges like that from Hurricane Katrina, which hit the U.S. coast in 2005, will there be as a result of global warming? New research from the Niels Bohr Institute show that there will be a tenfold increase in frequency if the climate becomes two degrees Celcius warmer.

The results are published in the Proceedings of the National Academy of Science (PNAS).

A University of Copenhagen release reports that tropical cyclones arise over warm ocean surfaces with strong evaporation and warming of the air. The typically form in the Atlantic Ocean and move toward the U.S. East Coast and the Gulf of Mexico. If you want to try to calculate the frequency of tropical cyclones in a future with a warmer global climate, researchers have developed various models. One is based on the regional sea temperatures, while another is based on differences between the regional sea temperatures and the average temperatures in the tropical oceans. There is considerable disagreement among researchers about which is best…
Since 1923, there has been a Katrina magnitude storm surge every twenty years.

Ten times as many Katrinas

“We find that 0.4 degrees Celcius warming of the climate corresponds to a doubling of the frequency of extreme storm surges like the one following Hurricane Katrina. With the global warming we have had during the 20th century, we have already crossed the threshold where more than half of all Katrinas are due to global warming,” explains Grinsted.

“If the temperature rises an additional degree, the frequency will increase by 3-4 times, and if the global climate becomes two degrees warmer, there will be about ten times as many extreme storm surges. This means that there will be a ‘Katrina’ magnitude storm surge every other year,” says Aslak Grinsted and he points out that in addition to there being more extreme storm surges, the sea will also rise due to global warming. As a result, the storm surges will become worse and potentially more destructive.